One of the well known environmental challenges nowadays is the handling of used tires. There are estimations that at least one billion tires are discarded around the world every year. These scrap tires are an ecological predicament in all countries in which automobiles and trucks are a standard mode of transportation. Over the years, many more tires cast off in monumental piles than recycled or burned. It is estimated that in the US alone there are in excess of 1 billion tires in illegal tire piles, generating dangerous conditions of uncontrollable fires, air pollution as well as health hazards.
To date, most discarded tires were destined to be burned, assisting in alleviating an unending energy crisis. However, since the recognition by meteorologists of pending earth warming trends, burning tires is quickly becoming unacceptable solution and in some countries even illegal. Also, to date, many of the waste tires are simply shredded and buried in landfills. This too has become an undesirable solution as more and more countries recognize the danger in underground buried tires or tire parts, due to the adverse effect on the diminishing underground supplies of fresh water. Finally, tire piles serve as breeding grounds to colonies of disease infected rodents and incubation hot beds for dangerous and deadly insects. It is therefore clear that recycling must be the only acceptable and sustainable solution to the increasing problem of scrap tires.
Recognizing all of the above, several attempts have been made to reduce the increasing number of scrap tires discarded annually by recycling them. Tire recycling has traditionally been accomplished using three distinctly different technologies:                All mechanical ambient grinding the rubber;        Cryogenically, freezing and crushing the rubber; and        Pyrolysis or microwave treatment to melt rubber.        
There are quite few aspects involved in the implementation of the second type of technology, namely, the cryogenically, freezing and crushing the rubber to produce granular rubber which may be used as a supplementary material in fuel or in road building, etc. One of the aspects involved in this technology is the step of exposing the crushed rubber to reduced temperatures e.g. to a point of embrittling the synthetic rubber.
Many conventional cryogenic recycling processes require the use of liquid nitrogen or solid carbon dioxide to lower the temperature of the material to be recycled to a point where a proceeding step of the process can yield a granular material such as a powder. However, such cryogenic processes are usually expensive to implement and to operate.
Many solutions were proposed in the past to improve this cooling step of the process. Few of these solutions are the following:
U.S. Pat. No. 4,273,294 discloses an improvement of conventional cryogenic grinding system incorporating an impact mill by providing means to allow at least 70% of the embrittled material entering the mill to bypass the mill's inlet and means to restrict the flow of the cold gas through the impact mill.
U.S. Pat. No. 5,408,846 describes a cooling device for lowering the temperature of rubber or polystyrene materials for recycling purposes. The cooling device has an input feeder which inputs the material to be treated into a cooling chamber. The cooling chamber is an elongated chamber. The cooling chamber receives cold air from an external air refrigeration unit and circulates that air within the chamber. The material input into the cooling chamber is circulated therein by a circulating shaft. After 15-20 minutes, the input material is discharged through an output on the opposite end of the cooling chamber. The material discharged temperature is −80° C. or lower.
U.S. Pat. No. 5,568,731 discloses an ambient air freezing system for producing chilled air in the cryogenic range of −120° C. to −180° C. without the use of cryogenic chemicals or other refrigerants.
U.S. Pat. No. 6,360,547 describes a method for cryogenically freezing materials, such as rubber, food, plastics by compressing ambient air to a first level, cooling the air back to an ambient temperature, compressing the air again, and then cooling the air followed by expanding the compressed air thereby cooling it down to cryogenic temperatures that is fed to the material to be processed.
U.S. Pat. No. 6,397,623 describes a cooling device in which the compressor and the expander are coupled to one crank shaft or interlocked crank shafts so as to use the expansion energy from the compressed air in the expander as an energy for compressing the outside air in the compressor, thereby reducing the running cost.
U.S. Pat. No. 7,125,439 discloses a method for providing clean air to an environment, by cooling incoming air, which may be contaminated with chemical, nuclear or biological contamination and removing water from the cooled air. The cooled air is passed through a regenerative pressure swing absorption system which removes the contaminants. The resulting, cleaned, air is expanded by an expander and is provided to the environment.